Implications for the management of submerged macrophytes in Canterbury lakes

Abstract

The thesis investigates several aspects of the management of submerged macrophytes. A survey of thirteen Canterbury lakes establishes submerged macrophyte species lists and plant community profiles for these lakes. Nuisance submerged macrophytes, other than Elodea canadensis, were not observed. The survey provides data for the establishment of a Geographical Information System (GIS) "lakes" database. The digital data for one of the lakes is utilised for modelling the (predicted) location of the nuisance submerged macrophyte Lagarosiphon major. It is argued that the model provides information that can then be used within a proactive management strategy for monitoring for the occurrence of the macrophyte in a lake. A concept of lake ecosystem management that integrates elements of protection, prevention, mitigation and restoration for lakes and macrophyte communities is introduced and discussed.

The legislation and institutional framework for the management of lakes and macrophytes is reviewed. In September 1993, the Biosecurity Act was passed, replacing several acts including the Noxious Plants Act. This Act has changed the concept of pest management in New Zealand. The main purpose of the Biosecurity Act is to enable the effective management or eradication of pests. Aquatic plants which under the previous legislation were managed as noxious weeds are not automatically defined as pests under the Biosecurity Act. The Biosecurity Act provides for a process of public evaluation of the necessity and desirability of management action through central or local government. The process for the development of a pest management strategy is reviewed with respect to aquatic macrophytes.